Determine most effective source(s) of immunosuppressive substances. Determine most expedient and efficient methods of purifying the immunosuppressive material. Evaluate various preparations using a variety of in vitro assays and thereby establish the range of action of these substances as well as assessing the comparative usefulness of each assay. Determine the optional route of administration and dosage for in vivo studies. Explore possible modes of action of the immunosuppressive substance(s).